1. Field of the Invention
The present invention relates to a portable rotary tool such as a disc grinder, a sander and a polisher.
2. Description of the Prior Art
A conventional rotary tool such as, for example, a disc grinder includes a body having a motor therein. A grinding wheel for rotation by the motor is mounted under the body at its forward portion. A handle is integrally formed with the rear portion of the body and includes therein a switch for controlling the motor. An operation member is mounted on the bottom of the handle or in the same direction as the grinding wheel. The operation member can be operated for starting the motor through the switch, so that the grinding wheel can be rotated for surface grinding of a work such as a metal material if the grinding wheel is one prepared for surface grinding.
In case that the disc grinder is to be used for cutting or grooving other works such as a concrete, a roof tile or other tiles, a brick and a stone, the grinding wheel is changed to one appropriate for cutting operation. In the practical operation by such grinding wheel appropriate for cutting, the rotary tool is positioned in such a manner that the grinding wheel abuts on the work substantially vertically to its surface. With such positioning of the rotary tool, the handle is turned sideways and therefore, the operation member is directed in a lateral direction (a direction perpendicular to the direction of movement of the grinding wheel for cutting into the work). This may cause difficulties in grasping the handle by an operator and in operating the operation member, so that the handling efficiency as well as the working efficiency may be decreased.
To resolve the above drawbacks, the prior art has proposed to provide a disc grinder having a motor housing and a gear housing which are connected with each other by screws. The motor housing includes a motor therein and is formed with a handle at its one end. The gear housing includes a gear mechanism therein for transmitting rotation of the motor to a grinding wheel. The motor housing and the gear housing can be fixed relative to each other with their positions angularly selectively displaced from each other at intervals of 90.degree. through removal of the screws. An operation member is mounted on the handle for operation of a switch for starting the motor and can be positioned on the side in a direction of movement of the grinding wheel for cutting into the work.
However, with this improved disc grinder, the screws must be completely removed and thereafter fastened again for each displacing operation. Such operation is very troublesome. Further, since the displacement is limited to the intervals of 90.degree., it does not satisfactorily meet various operation requirements.